1. Field of the Invention
The present invention relates to a vibrating plate according to the preamble of patent claim 1.
2. Description of the Related Art
Vibrating plates for soil compaction are known, and are made up in principle of a lower mass having a soil contact plate and an upper mass that is coupled to the lower mass by springs so as to be capable of motion, and that has a drive (e.g. an internal combustion engine or electric motor). The drive drives a vibration exciter device that appertains to the lower mass and that charges the soil contact plate.
The vibration exciter device introduces a directed vibration into the soil contact plate. The vibrating soil contact plate acts on the soil in order to compact it. In addition, the resultant overall force produced by the vibration exciter device can achieve propulsion in the longitudinal direction, as well as a steering of the vibrating plate. Because the principle of this design has long been known, more detailed description is not necessary here.
As a vibration exciter device, what is known as a one-shaft exciter, or plate compactor, is known, in which the drive rotationally drives an imbalance shaft that bears an imbalance mass. During its rotation, the imbalance shaft lifts the soil contact plate upward and forward in order to achieve forward motion. Subsequently, the soil contact plate is pressed downward by the action of the imbalance shaft, and strikes the soil that is to be compacted.
In larger vibrating plates, the vibration exciter device has two or three imbalance shafts that are coupled to one another mechanically, or with a positive fit, and that are situated parallel to one another. In a two-shaft exciter, such as that known for example from EP 0 358 744 A1, two imbalance shafts, each bearing an imbalance mass, are positively coupled to one another and are situated so as to be capable of rotation in opposite directions. The phase position of the imbalance
shafts relative to one another, it is possible to modify the direction of a resultant force vector, causing a change in the propulsion behavior. In particular, in this way it is possible to achieve forward and backward travel of the vibrating plate.
In a further development, the imbalance mass on one of the imbalance shafts is divided into two or more partial imbalance masses that can be adjusted relative to one another. If the partial imbalance masses on the imbalance shaft are adjusted asymmetrically to one another, a yaw moment can be produced around the vertical axis of the vibration exciter device, permitting steering of the vibrating plate. In the case of a symmetrical adjustment, in particular if, as in EP 0 358 744 A1, partial imbalance masses are fixedly attached to the relevant imbalance shaft and other partial imbalance masses are capable of being moved relative thereto, the resultant imbalance action can be adjusted, enabling setting of the resultant imbalance forces.
Standardly, in known vibration exciter devices the imbalance shafts are situated parallel to one another. In modern vibrating plates, it is therefore possible to achieve forward and backward travel, as well as to cause the vibrating plate to rotate in place or to travel on a curve. However, for some applications the user will desire a lateral movement of the vibrating plate, in order for example to enable travel behind lateral projections. When compacting soil on laterally inclined surfaces, the vibrating plate often drifts obliquely downward, so that the operator must orient the vibration plate obliquely in order to compensate this. However, in this case the soil at the upper and lower edge is compacted only by a corner of the soil contact plate, resulting in unsatisfactory compaction.
In these cases of application, it would be helpful for the vibrating plate to be capable of executing a lateral movement. However, in order to achieve such a lateral movement, the vibration exciter device would have to achieve a corresponding force action in the lateral direction.
From GB 1 166 025 A, another vibrating plate is known in which a vibration exciter device has four imbalance masses that are each capable of being driven rotationally about an axis of rotation.
From DE 100 53 446 A1, a vibrating plate is known that has an upper mass and a lower mass comprising a soil contact plate. The soil contact plate is charged by a vibration exciter device having two vibration exciters. Each of the vibration exciters is made up of two shafts, situated parallel to one another, that are positively coupled to one another and that rotate in opposite directions, each bearing an imbalance mass, and being situated so that their phase positions relative to one another can be adjusted. In contrast, the phase position of shafts of different vibration exciters is not adjustable.